Instrument panel lights / replacement

[rosie]

Hi
Did some work on my electrics last year which involved removing the instrument panel. After I put it back in none of the lights on the dials and digital clock work anymore. Not sure what I did wrong. I don't remember being rough with it.

Reading other threads suggests that the lights are powered by the blue&white wire on the white plug. I've had a fiddle with the connectors but no joy.
I've taken the instrument panel out again and can't see any obvious damage to the blue plastic PCB. I looked at threads showing how to pad out the plug so it connects better, but it doesn't look the same as my plug set up so I can't work out how to do it.

MOT is looming and presumably not being able to see how fast I'm going in the dark will be a fail?

A few questions:
Is there an easy way to test whether the fault lies in the panel or in the wiring loom/plug? I don't have a multimeter, just a test light. Can I test the blue&white wire to see whether power's getting to the plug with a test light somehow?

If the fault lies in the wiring prior to reaching the plug, someone mentioned that they managed to splice into another circuit to get power to the lights. Can anyone talk me through how to do this please?

If the fault lies on the panel itself is it possible to solder a wire onto the connectors on the PCB to bridge the fault?

If I need to replace the panel completely there are several panels on eBay, but with slightly different part numbers.
Mine is 191 919 059.
Are there any other part numbers that will also fit? A lot of them say they're a fit, but they only show kmph not mph, and don't have the same max speed on the dial.

Hope someone can help. Thanks so much.

[GT_II]

Yes, the speedo must light to pass the mot.

First question/test - do any other dash lights work eg cigarette lighter, heating controls? Do they brighten and dim with the brightness control?

[rosie]

Thank you.
So the cigarette lighter and the heating controls light haven’t worked for years which means I can’t test them, but you might be on to something.

About 12 years ago the circuit containing the cigarette lighter, central locking, stereo etc blew. No one could fix it. Last year I finally traced the fault to the cigarette lighter and disconnected it, which restored power to the rest of the stuff on that circuit. So far so good.

At the same time I removed the instrument panel to fix the lcd clock.
When I replaced the panel the clock illumination no longer worked. I assumed this was a problem with the instrument panel wiring.

But from what you’re saying I’m guessing that the clock illumination is linked to the cigarette lighter illumination? So maybe disconnecting the cigarette lighter has disconnected the instrument panel lighting as well?

If that is the case I guess the first thing to do is reconnect the broken cigarette lighter and see if the clocks illuminate again.

On holiday for a few days without any tools so I’ll give this a go next week and see what happens.

[mark1gls]

This may help, read rubjonny posts as he knows everything electrical unlike me… blue grey wire is the lighting circuit

https://vwgolfmk1.org.uk/forum/index.ph ... ot-working

Or Briano1234 posts.

https://vwgolfmk1.org.uk/forum/index.ph ... -and-gauge

[GT_II]

I doubt removing the cigarette lighter would be related, as the bulbs would be connected in parallel. I'll have a look at the wiring diagram at the weekend and see if I can identify a few terminals to check with your test light. However, chances are you'll also need a cheap multimeter from somewhere like Screwfix or Halfords so you can measure resistance/continuity as well as voltage.

[rosie]

Thanks guys.
I was hopeful for a minute it would be an easy fix - just reconnect the cigarette lighter til I made it through the mot. No such luck!
Currently have a mini torch blu-tacked to the dashboard. It looks great.

[GT_II]

Hi Rosie, the wiring for the instrument lighting is pretty straightforward, so just a very small number of checks with your test light should narrow down the fault.

First of all, are the warning lamps working normally? If so, it is safe to assume the earthing is OK as they share the same earth wire. Also, if the side lights and headlights are working, the main light switch is obviously receiving power.

The next thing to check is that the lighting switch is delivering power to the instruments via the variable instrument lighting control. The wiring diagram suggests this is via a terminal on the lighting switch feeding a fairly thin grey/blue wire. You should have 12V here when the lights are on and the lighting control turned to maximum brightness. If you connect your test lamp here (with the other test lamp lead connected to an earthing point), it should get brighter and dimmer as you turn the brightness knob on the switch. If you don't get that, the switch is likely faulty.

It looks like there is some kind of multi-way connector that joins the grey/blue wire from the lighting switch to multiple grey/blue wires on their way to each instrument lighting point (ashtray, heater control, cigarette lighter, lighting for various switches, radio as well as the instrument panel). The wire from there to the instrument panel is also grey/blue, so the terminal on the instrument panel is the next thing to check with your test light. If you get nothing there, suspect the multi-wire instrument lighting cluster of grey/blue wires somewhere behind the dash.

[rosie]

Oh wow. This is so helpful, thank you!
I’ll try this out when I get home on Thursday.
Thanks so much.

[rosie]

Well, it’s fixed. More by luck than judgement I think.

To start with I replaced the cigarette lighter, as this needed doing anyway. Strangely, once the cig lighter was in, the rev counter dial lit up again. The dimmer worked on both the cig lighter and the rev counter light.
Obviously this meant that the wiring to the bulbs was sound so I didn’t do any further checks on the wiring. Took out the instrument panel again and put in new bulbs and it’s all fixed.
Not sure why the cigarette lighter was involved (maybe someone else had previously done some diy wiring) but happy it’s done before the MOT!

I’m going to do a little post about how to replace the cigarette lighter cos it was a three day nightmare and I wish I’d known where the clips were. Maybe it’ll save someone else the misery.

Thanks so much GT-II for all your wiring research.